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Cheap and Easy “Precision Grinding” on the Lathe

I’ve worked out a quick and dirty holder for a dremel for my lathe toolpost. I made it out of 3d printed plastic, because the entire dremel is plastic. There is nothing to reference really on this curvy molded thing, no mounting posts to grab hold of (just one possible screw thread up front.) I made the holder to clamp it to a 0.5″ shank in two places with this inverted toroidal frustrum clamp thingy.


There isn’t a lot of tool-force on a grinding wheel, so my hope is that this plastic monstrosity will allow me to do precision grinding on my lathe. How precision? Well, with the standard (perhaps too coarse-grained) grindy-wheels that come with the dremel, I’m getting better surface finishes than with my random carbide cutter.

The grit is going to be a problem. I must keep it out of the rest of the machine at all costs. Best thing I’ve come up with so far is a flexible shop-towel barrier weighed down at the ends.

Pro-tip: When working with 3d printed plastic, you can stick PLA parts together very easily and very strongly with superglue and tower-hobby CA accelerator. The bond is almost as strong as the plastic itself. This allows you to do all sorts of lego-like things with parts you have to print out as multiple prints, due to the limitations of how the printing process works.

Also: Here is the download for the scad and stl files for putting the holder together. You may need to print different spacers cubes, depending on how things work out. Stick it all together with superglue.


Model Airplane 2022

Last Christmas, Mom and Dad got me two model aircraft kits. Over the past 3-4 months, I’ve been getting into the hobby.

This is my first attempt at building a model airplane. I’ve got ten tons of photos, which I’m going to place in a directory. Here are a few of them:

Here is the construction:

It’s certainly a process. I’ve learned a lot, and used about 25 tubes of superglue. You can see the learning curve from roughly the tail to the wings in the monokote job: It’s pretty rough at first.

What I didn’t want to do though was obsess over the construction over the course of years, painstakingly making a model of visual perfection. Because the next step is to fly this thing and probably crash it. (I’ll show it off to friends and family first, but planes were meant to fly.)

It’s orange so that I can find it again after it gets lost in the field behind my house. 😛

Announcing Riemann’s Lens

Announcing my upcoming virtual art display/simulation:

I will be publishing this on the Steam store, as soon as I can navigate the reams of paperwork and options, and figure out how to box up my program with their SDK.

Explore a wormhole!

Riemann’s Lens simulates the non-euclidean geometry and strange visual effects associated with a Riemannian wormhole. This interactive virtual art display allows you to fly around and through the wormhole, and render simple scenery in the euclidean space on either end. You can also adjust the size and geometry of the wormhole.

The simulation uses a compute shader to perform noneuclidean raytracing, and relies on the graphics card to perform some heavy computations. It has been developed on a machine with a GeForce GTX 1650, and it manages 2ish fps. Expect some lag. (Unless you have an awe-inspiring graphics card: Then brag about it.)

After I navigate the process and have the application shipped, I will post more about the math and logic behind the wormholes, the raytracer, and how to navigate in higher-dimensional noneuclidean space.



Apparently some explorers from the Falklands have recently found the wreck of the “Endurance” somewhere on the Antarctc seafloor. It was Shackleton’s failed expedition intending to cross the Antarctic on dogsleds, which ended up marooned in the ice surrounding the continent.

I remember once reading Jules Verne’s “Mysterious Island”, and remarking that it was the “anti-Lord-of-the-Flies” – the contrast in the picture of what men are asserted to be, and what their potential is, was stark.

This struck me in a very similar way. And it must be men like these that served as the inspiration for that brighter idea of human potential. It’s an interesting tale: Here you have people in lethal dire straights, and they behave rationally, gallantly, and honorably. They save themselves by extreme competence and self control. There is good faith and good will by everyone involved.

It’s a bit of an antidote to the present.


Okay, so a few things:

1. “Disinformatsiya” is rancid totalitarian duck-speak from an empire that imploded because *everything about it was a lie*. Transliterating it into English does not make it fresh and wholesome. “Misinformation” as a criterion for deciding which heretics to assault is such an integral part of Western civilization that it’s only found in all the best parts, like the Dark Ages, or the Reign of Terror, or … well, you get the idea.

2. “Lockdowns” are not a legitimate function of any government of free citizens. Lockdowns are what prison guards do during a prison riot. Do you think you are our jailers? Are the inmates of “your democracy” getting a little too rambunctious for your delicate sensibilities?

Your self awareness might not have been properly screwed down at the factory, but can you even *hear* yourselves?!

Spoiler alert!: The side that is hysterically censoring things in a desperate attempt to keep people from meeting and talking with each other, the side that angrily denounces the horrifying prospect of thoughts being independently formed in uncontrolled minds, while the jenga tower of their radiant and unquestionable truth makes ominous groaning noises are …. wait for it … NOT the good guys.

At this point you can lose, or you can lose, or you can maybe rethink your allegiance to people who are only going to be spurred to ever more desperate acts of oppression and evil, because they are stuck in the same dilemma you are.

1. You can “win”: Let’s suppose that your allies can successfully stamp on the collective human face forever. Never-mind that most people are never going to break the way you want them to: There will be the omnipresent danger that somewhere the light of understanding will dawn in someone’s eyes. Will it be accompanied by gratitude for those who were desperately trying to stop it from happening? When your victorious prison guards throttle the last human being in the last lockdown in the last gulag, where will that leave you? Yay.

2. You can lose: What if history doesn’t end? The video is never going away. The pictures are never going away. There are too many cameras in too many hands, too many people writing to each other, too many diaries being recorded. You can frantically erase things on all the “platforms” you control, but you can’t stop every letter or burn every book. Some people still use email. Hell, some people still use snail mail. Despite your feverish efforts, people are having beers at bars again and *talking*. At some point people are going to look back at the age of lockdowns and wonder whether your name was on any of the proposals howling for concentration camps and persecution. If mankind has a future worth bothering about, how do you think the would be prison-guards of humanity will be remembered? Will anyone care about their social credit score?

3. You can decide to forfeit this false position, either out of self-preservation, or because you suddenly remembered any relevant excerpt from all of human history and realize this is not going to go anywhere good. Maybe you haven’t hurt anyone yet. Or if you have, maybe you haven’t by your actions or cruel inaction killed anyone yet. Can’t say the same thing for your allies. Maybe no one will ever have to know. It’s not too late to get off this sinking ship. The faster this falls apart, the faster we can repair the damage and go somewhere worthwhile.

Shell World

Megastructure for sale! Get yer sci-fi megastructure here! Any authors that want to play with this idea welcome.

This is a write-up of an interesting idea I had back in August 2020. It’s for a particular type of sci-fi megastructure which should be stable (at least to back-of-the-envelope calculations) and would make an interesting setting/location/super-architecture-style for any authors who are interested. Not practical to build anytime soon, but interesting.
I’m not sure if this is original or not (I haven’t looked very hard.) If it is, I’m staking my claim! Publish or perish!

Shellworld Writeup

The basic idea, as described in the document, is that for a thick enough, large enough shell of matter, the force of gravity can balance internal pressure. The radius divides out, so this structure can be built without tensile stress to arbitrarily large radii, allowing the construction of massive amounts of habitable volume.

(PS: after some comments with James Cambias, it turns out this idea may not be original to me. Darn.)

Interesting Reading

Some interesting things I’ve been reading this year:

The Wright Bros by David McCollough is an interesting biography of the inventors of controlled heavier-than-air flight. One fascinating part was a reference to a speech made by Wilbur Wright at the Western Society of Engineers.

Link to my copy of the speech: “Some Aeronautical Experiments”, Wilbur Wright, 1901:


Link to where I obtained it from: Link
Link to the biography: The Wright Brothers, David McCollough

This is one example of what a first rate mind approaching a problem looks like. Wilbur makes it clear that the principal difficulty that he and his brother were tackling at Kitty-Hawk was the problem of controlling the vehicle while in the air. They built up the knowledge to do so with an extensive series of glider experiments. The experiment-heavy, experience heavy and iterative nature of their self-directed program contrasts with other efforts to build flying machines at the time: A large upfront investment made in an expensive machine which promptly crashes.

While the Wright Bros faced some pretty stiff incredulity and cynicism, most of that cynicism came from the world of the press and humanities. There was a fairly serious and supportive community of engineers who were making efforts to tackle the problem of heavier-than-air flight. (The Dayton Daily news refused to acknowledge their accomplishments, even as they were doing laps around Huffman Prarie. It fell to a Kentucky almanac run by a beekeeper to provide their first publicity!)

Book Workbench Python Scripts

Link to the scripts

Book Dumping and Book Binding Scripts

Aaron M. Schinder

18 Mar 2021


These scripts are intended to dump image files from pdfs and bind image files into pdfs. I wrote these primarily to convert Archive.org pdfs from the highly compressed format they use to less compressed but more readable pdfs built from the images.

The various Linux pdf readers have difficulty unpacking archive.org books. It’s a known problem. (It takes a very long time to load pages in whatever format or scheme archive.org uses internally)

The idea here is that hard drive space is cheaper than time, especially the loading time for the pages which may make paging and skimming through a book untenable. Paging through images can be done almost as fast as flipping through a physical book, so it doesn’t impede using them in a similar manner.


These tools were written to work on Linux (I don’t know if they’ll choke on Windows or not – may require some fiddling.)

They require the imagemagick command line tools (convert). Imagemagick may need the settings adjusted in /etc to avoid running out of memory.

They require pdfinfo and pdfunite and pdfinfo utilities from the poppler package/library.


ams_dumplargepdf.py : Dumps a pdf to image files in a directory named after the pdf file.

ams_dumpallbooks.py : Iterates over all pdf files in the directory it is called in.

ams_bindbook.py : takes all the image files in a directory and creates pdf fragments in stages. The pdfunite is called to concatenate all the pdfs into a new bound pdf. (Warning, it will name the pdf the same as the directory name: shuffle the files around to avoid an overwrite.)

ams_bindallbooks.py : takes all the book image directories and makes pdfs from them.

February 2021 Machine Shop Adventures

I recently bought some stepper motors from Sparkfun. I have two others floating around somewhere – they are of the NEMA-17 type (which specifies the face and shaft dimensions and mounting holes.) Mine are m-3 instead of 4-40 mounting holes, but otherwise standard.

I’ve often longed to do something with these motors – to build tools which can build better tools. My initial attempts to build motion stages involved buying stock parts from McMaster and attempting to 3d print all the connecting parts with a Makerbot Replicator 2X. Unfortunately the 3d printer has only about 0.04 inch accuracy, which isn’t enough to make motion stages that won’t bind, even when just aligning steel rods.

In my quest to become able to build serious tools, I’ve acquired a machine shop. I’m still not sure quite how to “climb the tech tree” from poor tools to better ones (more accurate, more precise). How *did* we get from hand tools to the bridgeport? How do you make something more accurate with something less accurate?

(edit, in response to the comment below: Since trying to build my first stages, I have done a little research on some of the steps in this process. I think one of the first ones involved Maudsley in England creating a lead screw using a self-propelled inclined knife on a flat slide climbing against a brass-rod workpiece. Also the Whitworth grinding proceess (which I’ve used myself on 3 pieces of steel – incredibly tedious) to get flat planes. That gave him a master leadscrew which eventually gave him a lathe, which gave some degree of positioning accuracy. I’m not surprised to see interferometry in there. Still haven’t read up on how they managed squareness. I’ll have to watch more of Dan Gelbart’s videos, since he’s been through the process I’ll eventually want to go through.)

Anyway, step 1 would be to build some motion stages so that I can build a CNC thing. (I’m thinking small, high-RPM/low tool force carbide bit CNC mill or something…)

Pencil scribbles

I am not my grandfather. My grandfather could do beautifully fine hand-drawings with drafting tools. I’ve inherited this old map of his alma-mater, Tri-State College done by him during a course on engineering drawing (will include eventually). Thomas French, Engineering Drawing – it was tucked into his textbook.

Hand drawings are useful: They’re faster than CAD when you’re still trying to figure things out, and may be entirely sufficient to plan out a part. Here is that hand-drawing cleaned up and colorized for visual interest.

The big idea

Anyway, this was the plan. I ordered a bunch of stock parts from McMaster, I made one attempt last week to cut the dovetail slide from a piece of aluminum. I figured, aluminum is softer. I can practice on it without blowing up my tools. That worked until I attempted to use the dovetail cutter. Advancing about 50 thousandths per step (way too fast), without using adequate lubricant (Dad suggests WD-40 when cutting aluminum. *Not* when cutting steel – then it would carbonize and work-harden the part.), I ended up blowing up the dovetail cutter in my face.

Aluminum doorstop that also handily stabs you

I decided, since getting the part to that state took 5 hours, to bite the bullet and just do it in steel this time. 5 hours of end milling and a nautical ton (it’s an English unit, honest!) of chips later, I had the slide squared and the square-cuts done with nice surface finish. Can’t feel any roughness with my fingernail (the fingernail test).

Beautifully squared piece of steel, ready for wrecking

I painted some Dykem blue layout fluid on the corner in an attempt to see my cuts.

The wax goop on the tool was difficult to pry off. Tools are often dipped in this waxy crud to prevent corrosion. I managed to get it off by submerging the tool in a pot of boiling water – this worked and allowed me to easily remove the wax, which is important when attempting to get the tool into a precise starting position.

This shows the tool ready to cut. This time I was paranoid, listened very carefully to the horrible noises the cutter made as I advanced, and probably saved myself from a blowup at the very end. I advanced about 5 thousandths per step towards the end, and only about 0.2200 of my planned 0.2500. On the last cut the tool made a horrible racket on the last inch of the cut. On attempting to start the back-side, the tool wouldn’t cut at all. It had dulled itself fairly quickly.

It was a high-speed steel (as opposed to the cobalt steel) 45 degree, 1 3/8″ diameter dovetail cutter from McMaster Carr. (Not sure if I recommend them – they dull too fast.) I’m waiting on a new cutter to finish the job, and some carbide inserts for a 60 degree insert dovetail cutter from Dorian Tool by way of MSC.

One random trick that I had heard about watching youtube videos of people doing far more intricate things: Apparently when cutting steel, you can pay attention to the color of the chips. Straw-yellow means that the chips are getting somewhat hot as you are cutting. If they start turning blue, it means you are work-hardening the part and generating too much heat, and need to proceed (with more coolant, less agressively, at lower speeds).

South Bend Lathe Model SBL400 Parts List

I recently purchased a used metal lathe: A South Bend model SBL-400, from Jones Machinery in Cinncinatti.

Unfortunately, I did not have an opportunity to inspect the lathe very closely until now, and there are too many things wrong with it to make much use of it. It’s been used hard over the years, and the cross-slide skips. There’s some sort of collet holder wedged into the spindle and I’m not sure how to remove it. The foot-break won’t engage. Etc.

It’s a good model, but this one would be dangerous to attempt to operate, and I’d have to sink a lot of money into repair.

As part of the purchase, I bought a parts list that I couldn’t find anywhere online in digital form. Here is the parts list for anyone else out there lucky enough to have an SBL-400 in better working order:

SBL Parts List